Skid steer loader boom and bucket controls

ABSTRACT

An electronic control system for a machine having a boom assembly and an implement assembly. A microprocessor is provided having an input and generating first and second output signals. A first electrohydraulic valve is connected to receive the first output signal from the microprocessor, and connected to position the boom assembly in response to the first output signal. A second electrohydraulic valve is connected to receive the second output signal from the microprocessor, and connected to position the implement assembly in response to the second output signal. A boom position sensor is disposed on the boom assembly or the implement assembly and connected to send a boom position input signal to the microprocessor, the microprocessor being connected to receive the boom position input signal and generate at least one of the first output signal and the second output signal, thereby controlling a position of the implement assembly relative to the boom assembly.

FIELD OF THE INVENTION

[0001] This invention pertains to devices or machines having a hydraulicboom and bucket assembly that is operatively controlled by an electroniccontrol system, and to the electronic control system itself. Moreparticularly, the invention relates to a hydraulic boom and bucketassembly, such as would be mounted to a work vehicle or skid steerloader, wherein the hydraulic boom and bucket assembly is operativelycontrolled by a computer-controlled electronic control system carried bythe work vehicle or skid steer loader.

BACKGROUND OF THE INVENTION

[0002] Skid steer loaders are work vehicles that include four wheelsrotatably mounted to a frame, an engine mounted on the frame andconnected by a transmission to rotate at least two wheels, a cabcompartment mounted on the frame that includes a seat for an operator,manual controls and a display panel disposed in the cab compartment, aboom assembly rotatably mounted on the frame and connected to a pair ofhydraulic boom cylinders for moving the boom assembly, and an implementassembly connected to the boom assembly. Typically, one or morehydraulic cylinders are used to manipulate the implement assembly.Preferably, the implement assembly is a bucket assembly, wherein theimplement is a bucket and a pair of hydraulic bucket cylinders is usedto move the bucket assembly. Other types of work vehicles that aresimilar to skid steer loaders include tractors and bulldozers.

[0003] To operate the hydraulic boom cylinders and the hydraulic bucketcylinders, an operator in the cab manipulates either hand or footcontrols. The skid steer loader, or similar work vehicle, includes anelectronic control circuit system that includes an onboard computer,microprocessor, or controller. For the purposes of this disclosure, acomputer, microprocessor, or controller are considered to be equivalentand interchangeable elements. The onboard computer operates solenoids ofelectrohydraulic valves that activate the hydraulic boom and bucketcylinders. To ensure the safe operation of the work vehicle, theelectronic control system can be configured to include a safety featurethat enables the operation of the electrohydraulic solenoid valves ofthe hydraulic cylinders only when a safety switch circuit is properlyactivated. One such electrical circuit forming the controller of a boomsolenoid valve is disclosed in U.S. Pat. Nos. 4,856,612 and 4,871,044 toClevenger, Jr. et al. and to Strrosser et al. respectively, both ofwhich are incorporated herein in their entirely by reference. In theelectrical circuit of this controller, there is a built in safetyfeature wherein the controller cannot operate the boom solenoid valveunless both the belt switch and a seat switch were activated by thesimultaneous conditions of (a) having the seat belt restraint mechanismengaged and (b) having an operator sitting in the operator's seat.

[0004] U.S. Patent Application Publication U.S. 2001/0007087 A1 toBrandt et al., which is also incorporated herein by reference for all itdiscloses, teaches a computer based control system for a skid steerloader that includes a computer receiving inputs from a control panel,various sensors, hand grip and foot pedal inputs, and a seat bar sensor.The computer generates outputs to hydraulic actuators and associatedvalves, and to electromechanical devices.

[0005] The prior work vehicles have several drawbacks. First, it isdesirable to permit an operator to select enablement of either hand orfoot controls for manipulating the boom assembly and the bucketassembly. In addition, because the boom assembly and the bucket assemblyare manually controlled separately, the operator can mistakenly dump outthe contents of the bucket inadvertently. In some cases, such as whenoperating a fork lift, it may be an advantage to manipulate the boomassembly while maintaining a constant angular bucket position (i.e.horizontal) of a fork lift work implement to the ground or to the workvehicle. Therefore, it would be beneficial to provide an electroniccontrol system for a work vehicle that includes a multi-modeself-leveling bucket option for maintaining a constant angular bucketposition of the bucket to the ground, to the work vehicle, or to somereturnable position of advantage.

[0006] The present invention endeavors to provide an improved electroniccontrol system for a work vehicle, or like machine, having a boomassembly and a work implement assembly connected to the boom assembly sothat the improved electronic control system of the present inventionmaintains the benefits of the prior electronic control systems whileovercoming the drawbacks of these prior control systems.

[0007] Accordingly, one object of the present invention is to overcomethe disadvantages of the prior art electronic control systems for workvehicles and like machines.

[0008] Another object of the present invention is to provide anelectronic control system for work vehicles, and like machines, thatincludes a safety switch to prevent enablement of the solenoids of theboom assembly and the bucket assembly unless an operator is sitting inthe operator's seat and/or the seat belt restraint device has beenproperly secured.

[0009] Another object of the present invention is to provide anelectronic control system for work vehicles, and like machines, thatincludes a multi-mode self-leveling bucket option for maintaining aconstant angular bucket position of the bucket to the ground, to thework vehicle, or to some desired retrievable position of advantage.

[0010] Another object of the present invention is to provide anelectronic control system for work vehicles, and like machines, thatpermits the selection and enablement of either hand or foot controls tomanipulate the boom assembly and the implement assembly.

[0011] Another object of the present invention is to provide anelectronic control system for work vehicles, and like machines, that ispractical and cost effective to manufacture.

[0012] Another object of the present invention is to provide anelectronic control system for work vehicles, and like machines, that isboth durable and reliable.

[0013] Of course, while the electronic control system for work vehicles,and like machines, will be described for use in skid steer loaders andlike machines, another object of the present invention is to provide anelectronic control system for a machine having a boom assembly and animplement assembly connected to the boom assembly, wherein the machinecan be a self-propelled machine or a stationary machine.

SUMMARY OF THE INVENTION

[0014] In accordance with the above objectives, the present inventionprovides a first preferred embodiment that is an electronic controlsystem for a machine having a boom assembly and an implement assemblyconnected to the boom assembly, the control system comprising: (a) amicroprocessor having an input and generating first and second outputsignals; (b) a first electrohydraulic valve connected to receive thefirst output signal from the microprocessor, wherein the firstelectrohydraulic valve is connected to position the boom assembly inresponse to the first output signal; (c) a second electrohydraulic valveconnected to receive the second output signal from the microprocessor,wherein the second electrohydraulic valve is connected to position theimplement assembly in response to the second output signal; and (d) aboom position sensor disposed on the boom assembly or the implementassembly and connected to send a boom position input signal to themicroprocessor, wherein the microprocessor is connected to receive theboom position input signal and generate at least one of the first outputsignal and the second output signal, thereby controlling a position ofthe implement assembly relative to the boom assembly.

[0015] In accordance with a second preferred embodiment, the firstpreferred embodiment is modified to include a safety switch circuitconnected to send a first activation signal to the microprocessor,wherein the microprocessor is unable to generate the first output signaland is unable to generate the second output signal until themicroprocessor receives the first activation signal generated by thesafety switch circuit.

[0016] In accordance with a third preferred embodiment, the secondpreferred embodiment is further modified so that the safety switchcircuit includes a seat belt having male and female ends so that thesafety switch circuit sends the first activation signal when the maleand female ends are secured together.

[0017] In accordance with a fourth preferred embodiment, the secondpreferred embodiment is further modified so that the safety switchcircuit is connected to an operator's seat so that the safety switchcircuit sends the first activation signal when an operator is sitting inthe operator's seat.

[0018] In accordance with a fifth preferred embodiment, the secondpreferred embodiment is further modified so that the safety switchcircuit includes a seat belt having male and female ends and the safetyswitch circuit is connected to an operator's seat so that the safetyswitch circuit sends the first activation signal when the male andfemale ends of the seat belt are secured together and an operator issitting in the operator's seat.

[0019] In accordance with a sixth preferred embodiment, the firstpreferred embodiment is further modified so that the implement assemblyis selected from the group consisting of a pallet forks lift assemblyand a loader bucket assembly.

[0020] In accordance with a seventh preferred embodiment, the firstpreferred embodiment is further modified to include a right hand stickimplement control sensor disposed to sense a position of a right handcontrol; a left hand stick boom control sensor disposed to sense aposition of a left hand control; a right foot pedal implement controlsensor disposed to sense a position of a right foot pedal control; and aleft foot pedal boom control sensor disposed to sense a position of aleft foot pedal control, where each control sensor is connected to sendelectronic signals to the microprocessor.

[0021] In accordance with an eighth preferred embodiment, the seventhpreferred embodiment is further modified to include a hand/foot controlsselector switch connected to send a first enabling signal to themicroprocessor, wherein the first enabling signal enables themicroprocessor to generate first and second output signals in responseto electronic signals received from the right hand stick implementcontrol sensor and the left hand stick boom control sensor, andelectronic signals received from the right foot pedal implement controlsensor and the left foot pedal boom control sensor have no effect on thefirst and second output signals generated by the microprocessor.

[0022] In accordance with a ninth preferred embodiment, the eightpreferred embodiment is further modified so that the microprocessor useselectronic signals received from the right hand stick implement controlsensor to generate the second output signal and electronic signalsreceived from the left hand stick boom control sensor to generate thefirst output signal.

[0023] In accordance with a tenth preferred embodiment, the eighthpreferred embodiment is further modified so that the hand/foot controlsselector switch is connected to send a second enabling signal to themicroprocessor, wherein the second enabling signal enables themicroprocessor to generate first and second output signals in responseto electronic signals received from the right foot pedal implementcontrol sensor and the left foot pedal boom control sensor, andelectronic signals received from the right hand stick implement controlsensor and the left hand stick boom control sensor have no effect on thefirst and second output signals generated by the microprocessor.

[0024] In accordance with an eleventh preferred embodiment, the seventhpreferred embodiment is further modified to include a hand/foot controlsselector switch connected to send a first enabling signal to themicroprocessor, wherein the first enabling signal enables themicroprocessor to generate first and second output signals in responseto electronic signals received from the right foot pedal implementcontrol sensor and the left foot pedal boom control sensor, andelectronic signals received from the right hand stick implement controlsensor and the left hand stick boom control sensor have no effect on thefirst and second output signals generated by the microprocessor.

[0025] In accordance with a twelfth preferred embodiment, the eleventhpreferred embodiment is further modified so that the microprocessor useselectronic signals received from the right foot pedal implement controlsensor to generate the second output signal and electronic signalsreceived from the left foot pedal boom control sensor to generate thefirst output signal.

[0026] In accordance with a thirteenth preferred embodiment, theeleventh preferred embodiment is further modified so that the hand/footcontrols selector switch is connected to send a second enabling signalto the microprocessor, wherein the second enabling signal enables themicroprocessor to generate first and second output signals in responseto electronic signals received from the right hand stick implementcontrol sensor and the left hand stick boom control sensor, andelectronic signals received from the right foot pedal implement controlsensor and the left foot pedal boom control sensor have no effect on thefirst and second output signals generated by the microprocessor.

[0027] In accordance with a fourteenth preferred embodiment, the eighthpreferred embodiment is further modified to include a status displaydisposed within an operator's cab, the cab being integral to themachine, wherein the status display includes a first light sourceconnected to receive third output signals from the microprocessor, andthe microprocessor sends the third output signals to control flashing ofa light source until the microprocessor generates the first enablingsignal.

[0028] In accordance with a fifteenth preferred embodiment, the eleventhpreferred embodiment is further modified to include a status displaydisposed within an operator's cab, the cab being integral to themachine, wherein the status display includes a first light sourceconnected to receive third output signals from the microprocessor, andthe microprocessor sends the third output signals to control flashing ofa light source until the microprocessor generates the first enablingsignal.

[0029] In accordance with a sixteenth preferred embodiment, the secondpreferred embodiment is further modified to include a status displaydisposed within an operator's cab, the cab being integral to themachine, wherein the status display includes a first light sourceconnected to receive third output signals from the microprocessor, andthe microprocessor sends the third output signals to control flashing ofa light source until the microprocessor receives the first activationsignal from the safety switch.

[0030] In accordance with a seventeenth preferred embodiment, the firstpreferred embodiment is further modified to include an implement angleposition sensor disposed to sense an angular position of the implementassembly relative to the machine and generate an implement angleposition input signal, wherein the microprocessor is connected toreceive the implement angle position input signal from the implementangle position sensor; and optionally, a tilt sensor disposed on themachine to sense a position of the machine relative to the horizon andgenerate a tilt input signal, wherein the microprocessor is connected toreceive the tilt input signal from the tilt sensor, and wherein themicroprocessor generates at least one of the first output signal and thesecond output signal in response to receiving the boom position inputsignal, the implement angle position input signal, and optionally thetilt input signal.

[0031] In accordance with an eighteenth preferred embodiment, theseventeenth preferred embodiment is further modified so that themicroprocessor is programmed to perform an implement self-levelingfunction operable in three modes in response to receiving the boomposition input signal, the implement angle position input signal, andoptionally the tilt input signal, wherein the first mode is a null mode,the second mode is a return-to-dig mode, and the third mode is a horizonreferencing mode, and the electronic control system further includes animplement leveler mode selection switch connected to send a modeselection signal to the microprocessor, wherein the microprocessorselectively operates in one of the null mode, the return-to-dig mode,and the horizon referencing mode in response to receiving the modeselection input signal from the implement leveler mode selection switch.

[0032] Further objects, features and advantages of the present inventionwill become apparent from the Detailed Description of PreferredEmbodiments, which follows, when considered together with the attacheddrawings.

BRIEF DESCRIPTION OF THE DRAWINGS

[0033]FIG. 1 is a schematic side perspective view of a work vehicle inaccordance with the present invention with the hydraulically activatedmovement of the boom assembly being shown in phantom.

[0034]FIG. 2 is a cross sectional, cut away side view of the cab of thework vehicle shown in FIG. 1.

[0035]FIG. 3 is a schematic drawing of the electronic control system fora work vehicle having a boom assembly and an implement assemblyconnected to the boom assembly in accordance with the present invention.

[0036]FIG. 4 is a schematic side perspective view of a work vehicle inaccordance with the present invention illustrating movement of the boomassembly and loader bucket implement in the “return-to-dig” mode.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0037]FIG. 1 shows a compact work vehicle 10, such as a skid steerloader or other like work vehicle, that includes a cab compartment 20 onthe vehicle. Typically, work vehicle 10 includes a body 12 that ismounted on four wheels 13 (only two shown) suitably connected to berotated by a transmission. The transmission is powered by an enginedisposed in engine housing 14, located on the body 12. One skilled inthe art would realize that the work vehicle 10 could be a trackedvehicle, a vehicle mounted on rails, or could be a machine mounted to astationary frame without departing from the scope of the presentinvention.

[0038] Work vehicle 10 includes a boom arm assembly 17 that is pivotallyconnected to the body 12 at one end, and that is pivotally connected atits opposite end to a work implement 16, such as a loader bucket 16 b,pallet forks attachment 16 a, or other useful tool. As shown in FIG. 1,boom arm assembly 17 can be raised and lowered between a lower positionA and an upper position B (shown in phantom) through a range of motionusing hydraulic power provided by a pair of hydraulic boom cylinders 19(only one shown) of a hydraulic circuit (not shown) so that theimplement 16 can be used to perform its intended function. The hydrauliccircuit also powers one or more hydraulic implement cylinders 18 (onlyone shown) for moving and/or activating the implement 16. In the casewhere the work vehicle 10 is a skid steer loader, the implement 16 is,for example, a loader bucket 16 b and there is a pair of bucketcylinders (only one cylinder shown) for moving and/or activating theloader bucket as illustrated in FIG. 4.

[0039] As shown in FIG. 2, inside of cab compartment 20, there is anoperator's seat 22 upon which an operator sits while operating the workvehicle 10. Seat 22 is equipped with a seat pressure sensor or seatswitch 24, such as described in U.S. Pat. Nos. 4,856,612 and 4,871,044,both of which are incorporated herein by reference for all theydisclose. When seat 22 is empty, the seat switch 24 is open and when anoperator sits in the seat 22, then the seat switch 24 is pressed into aclosed state. Seat 22 is also equipped with a restraint seat belt switch26 that includes a male end 28 that matingly secures to female end 30.When male end 28 and female end 30 are matingly secured together, thenseat belt switch 26 is in the closed state. When male end 28 and femaleend 30 are not secured together, then scat belt switch 26 is in the openstate.

[0040] Cab compartment 20 also includes a display, such as, for example,a Total Control System display (“TCS display”) 70 for displaying variouslight indicators, LEDs, gauges and the like, to inform the operator ofthe status of the various monitored systems carried by the work vehicle10. Cab compartment 20 also has a pair of foot control pedals 50 (onlyone pedal shown) and a pair of hand grip controls 60 (only one gripshown) for operating the boom arm assembly 17 and the implement 16.

[0041]FIG. 3 illustrates electrical connections between the variouscomponents of the electronic control system 90 in accordance with thepresent invention. Electronic control system 90 is carried by the workvehicle 10 and includes an on board controlling microprocessor (alsoreferred to as the “controller”) 110 connected to exchange data with amemory storage device 111. Preferably, memory storage device 111 is anon-volatile memory that stores the neutral positions of the footcontrol pedals 50 and the hand grip controls 60, and other data asdescribed below. Although controller 110 and memory storage device 111are preferably separate structures, controller 110 can be constructed toincorporate the memory storage device without departing from the scopeof the invention.

[0042] Controller 110 is connected to receive electronic signal inputsfrom the following devices: operator “seat belt switch and seat switch”circuit 120, right hand stick implement control and position sensor 122,left hand stick boom control and position sensor 124, right foot pedalimplement control and position sensor 126, left foot pedal boom controland position sensor 128, hand/foot controls selector switch 132, vehicletilt sensor 134, implement leveler mode selection switch 136, boomposition sensor 140, and implement angle position sensor 142. Althoughmany different types of controllers are suitable for use as thecontroller 110 in system 90 of the present invention, microcontrollerC167CR manufactured by Infineon Technologies AG (Germany) isparticularly well suited for use in the present system environment.

[0043] The operator “seat belt switch and seat switch” circuit 120 is anelectronic circuit that generates an enabling signal when seat beltswitch 26 and seat switch 24 are in the closed state (i.e., an operatoris sitting in seat 22 and the male end 28 of seat belt switch 26 issecured to the female end 30). Controller 110 is not enabled to producecontrol output signals until the seat belt switch and seat switchcircuit 120 sends an enabling electronic signal to the controller. Seatbelt switch 26 and seat switch 24 are incorporated into the “seat beltswitch and seat switch” circuit 120 as indicated in FIG. 3. One suchcircuit suitable for use as the seat belt switch and seat switch circuit120 is disclosed in U.S. Pat. No. 4,871,044 to Strosser et al., which isincorporated herein by reference for all it contains.

[0044] The right hand stick implement control and position sensor 122 isan electronic sensor that sends signals to controller 110 reporting theposition of the right hand grip control 60. The position of the righthand grip control 60 is sensed by sensor 122 that generates an outputsignal sent to controller 110. Controller 110 processes the signalsprovided by sensor 122 and uses the information to operateelectro-hydraulic implement cylinder valve 152, thereby controlling theposition of implement 16 relative to boom assembly 17 as describedbelow.

[0045] The left hand stick boom control and position sensor 124 is anelectronic sensor that sends signals to controller 110 reporting theposition of the left hand grip control 60. The position of the left handgrip control 60 is sensed by sensor 124 that generates an output signalsent to controller 110. Controller 110 processes the signals provided bysensor 124 and uses the information to operate electro-hydraulic boomcylinder valve 150, thereby controlling the position of boom assembly 17relative to the work vehicle 10 as described below.

[0046] The right foot pedal implement control and position sensor 126 isan electronic sensor that sends signals to controller 110 reporting theposition of the right foot control pedal 50. The position of the rightfoot control pedal 50 is sensed by sensor 126 that generates an outputsignal sent to controller 110. Controller 110 processes the signalsprovided by sensor 126 and uses the information to operateelectro-hydraulic implement cylinder valve 152, thereby controlling theposition of implement 16 relative to boom assembly 17 as describedbelow.

[0047] The left foot pedal boom control and position sensor 128 is anelectronic sensor that sends signals to controller 110 reporting theposition of the left foot control pedal 50. The position of the leftfoot control pedal 50 is sensed by sensor 128 that generates an outputsignal sent to controller 110. Controller 110 processes the signalsprovided by sensor 128 and uses the information to operateelectro-hydraulic boom cylinder valve 150, thereby controlling theposition of boom assembly 17 relative to the work vehicle 10 asdescribed below.

[0048] Preferably, the control and position sensors 122, 124, 126 and128 generate analog output signals ranging from +0.5 to +4.5 V.

[0049] The hand/foot controls selector switch 132 is an electronicswitch that operates to send input signals to controller 110, andcontroller 110 uses this input signal to enable either the hand gripcontrols 60 or the foot control pedals 50. Thus, in a first state,switch 132 has enabled or activated system 90 to use the hand controls60, and disables or deactivates the foot control pedals 50. With switch132 in the first state, only the right and left hand controls 60 can beused to effect operation of the electro-hydraulic valves 150 and 152 ofthe boom cylinders 19 and the implement cylinders 18, respectively. In asecond state, switch 132 has enabled or activated the foot pedals 50,and disables or deactivates the hand controls 60. With switch 132 in thesecond state, only the right and left foot pedals 50 can be used toeffect operation of the electro-hydraulic valves 150 and 152 of the boomcylinders 19 and the implement cylinders 18, respectively.

[0050] Preferably, switch 132 is constructed as a pressure sensingswitch that sends a generic input signal to controller 110. In addition,controller 110 operates functionally to provide system 90 with a thirdstate, wherein neither the hand controls 60 nor the foot pedals 50 areenabled, with or without an input signal from sensor 132. In otherwords, when switch 132 is used to select the third state, the boomassembly 17 and the implement 16 are not operable. This condition isdesirable when accidental operation of the boom assembly 17 andimplement 16 is to be avoided, such as when driving the work vehicle 10a relatively long distance from one work site to another work site.However, when the work vehicle 10 is initially started up, controller110 is programmed to initiate system 90 in the third state (i.e.,neither hand controls 60 nor foot pedal controls 50 are enabled).

[0051] As mentioned, controller 110 is pre-programmed so that uponstart-up of the work vehicle 10, the system 90 is in the third state. Inother words, at start-up neither the hand controls 60, nor the footpedals 50, are enabled until switch 132 is pressed or operated. Whenswitch 132 is first operated after start-up, the signal sent tocontroller 110 is used to enable either the hand controls 60 or thepedal controls 50, depending upon which set of controls was lastenabled. In other words, controller 110 uses information stored inmemory 111 that identifies which set of controls, either 60 or 50, werelast enabled, and uses this information to preferentially enable thatset of controls after start-up when switch 132 is first activated. Thus,whenever switch 132 is operated, the controller 110 sends output signalsto memory storage device 111 so that the system 90 can recall the lastenabled state in operation, either the first or second state, prior toshutting down the system when the work vehicle 10 is turned off.

[0052] Vehicle tilt sensor 134 is an electronic sensing circuit thatprovides signal output to controller 110 that indicates the relativeorientation of the work vehicle 10 with respect to the Earth's horizon.In other words, sensor 134 senses the position of the work vehicle 10relative to the horizontal plane of the Earth's horizon and inputs thisinformation into controller 110 so that the controller can use theinformation to make automatic adjustments in the operation of theelectro-hydraulic valves 150 and 152 effecting movement of the boomassembly 17 and the implement 16, respectively. Acceptable devices foruse as the vehicle tilt sensor 134 include a linear mercury switch, or acapacitive fluid tilt sensor. However, it has been determined that MicroElectro Mechanical Systems (“MEMS”), which utilize micromachined angularrate sensor technology, provide excellent gyroscopic inertial sensorsthat are superior for use as the vehicle tilt sensor 134. Micromachinedangular rate sensors, such as the BEI Gyrochip™ II (Part Nos.QRS14-0XXXX 102 and QRS14-0XXXX 103, Systron Donner Inertial Division,Concord, Calif., www.systron.com), measure angular rotation rates usinga solid-state monolithic quartz sensing element. These micromachinedangular rate sensors are reliable and durable, having an operatingtemperature of −40° C. to +85° C. and tolerate shock of 200 g.

[0053] The boom position sensor 140 is an electronic sensor that iscarried by the boom assembly 17 and provides an input signal to thecontroller 110 indicating the height of the boom assembly relative tothe work vehicle 10.

[0054] Optionally, system 90 can be provided with an implement angleposition sensor 142, which is especially useful when the implement 16 isa loader bucket. The implement angle position sensor 142 is anelectronic sensor that is carried by the boom assembly 17 and thatprovides an input signal to the controller 110 indicating the angularposition of the implement 16 relative to the work vehicle 10.

[0055] Controller 110 is pre-programmed with an automatic implementself-leveling feature, which is most useful when implement 16 is aloader bucket 16 b or a pallet forks lift attachment 16 a. The automaticimplement self-leveling feature is a programmed function of controller110, wherein the controller operates to receive input from vehicle tiltsensor 134, boom position sensor 140, and optionally implement angleposition sensor 142, and uses the inputted signals to generate outputsignals to electro-hydraulic valve 152 that effects operation ofimplement cylinders 18 and movement of the implement 16 relative to theboom assembly 17. In this manner, controller 110 can automaticallycontrol the relative orientation of the implement 16 relative to theboom assembly 17. The controller 110 is programmed to operate in thisautomatic self-leveling feature in three modes: (a) the null mode, (b)the “return-to-dig” mode, and (c) the “horizon referencing” mode. Theimplement leveler mode selection switch 136 is an electronic switch thatoperates to select either one of the three modes. In addition, system 90can be constructed so signal information used to select and activate thedesired self-leveling mode can be stored by the memory storage device111. In this manner, system 90 would recall the last implementself-leveling mode in operation upon shutdown of the work vehicle 10 sothat the work vehicle begins in this mode upon start-up of the workvehicle; however, in a preferred embodiment of the invention system 90defaults to the null mode upon start-up of the work vehicle.

[0056] The three automatic self-leveling modes will now be described.The null mode is the mode wherein the automatic self-leveling feature isdisabled. In other words, when the controller 110 is operating in thenull mode there is no self-leveling feature in effect and implement 16will be positioned relative to the boom assembly 17 as directed by thepositions of the enabled left foot pedal 50 or enabled left hand control60. The null mode may be activated using switch 136, and/or it may bethe default mode of system 90 upon activation of the work vehicle 10.

[0057] In the return-to-dig mode, as illustrated in FIG. 4, controller110 operates to return the orientation and position of implement 16 andboom assembly 17 to a fixed, memorized orientation and position relativeto the work vehicle 10. In other words, at the moment the return-to-digmode is activated, controller 110 receives signals from boom positionsensor 140 and implement angle position sensor 142 and stores thisinformation in memory storage device 111, thereby memorizing theposition and orientation of the boom assembly 17 and the implement 16.This memorized position and orientation is referred to the“return-to-dig” position, although it need not be a position andorientation used for digging. Subsequently, the operator is free to moveimplement 16 and boom assembly 17 using either the enabled hand controls60 or the enabled foot pedal controls 50, depending upon which pair ofcontrols have been selectively enabled by the operator as describedabove. In the return-to-dig mode, the operator can return implement 16and the boom assembly 17 to the memorized “return-to-dig” position bypressing a “return-to-dig” switch button 80 disposed on one of the handcontrols 50. This button would be connected to operate a switch that isconnected to send a signal to controller 110 informing the controller tooperate electro-hydraulic valves 150, 152 to return the implement 16 andboom assembly 17 back to the return-to-dig position based on theinformation stored in the memory storage device 111.

[0058] As an illustrative example, as shown in FIG. 4, the operator canactivate the return-to-dig mode using switch 136 when the implement 16and boom assembly 17 are in a first position, such as the position andorientation represented at C. The operator can subsequently move theimplement 16 and boom assembly 17 using either enabled hand controls 60or enabled foot pedal controls 50. At any time while implement 16 andboom assembly 17 are in a second position, such as the exemplaryposition and orientation represented at D, the operator can press the“return-to-dig” switch button 80, thereby activating the controller 110to return the implement and the boom assembly from position D back tothe selected return-to-dig position C. One of ordinary skill in the artwould appreciate that FIG. 4 is merely exemplary, and that thereturn-to-dig position represented by C could be any position within therange of motion attainable by the controlled movement of implement 16and boom assembly 17. Furthermore, the second position D could be anyother attainable position within the range of motion of the implementand the boom assembly. The benefit of having the return-to-dig mode isthat, while engaged in digging or any other repetitive movement of theimplement and boom assembly, the operator can, at the touch of a button,return the implement and boom assembly to a desired first position fromany other second position.

[0059] Operation of switch 136 places system 90 into the return-to-digmode. Although FIG. 4 illustrates implement 16 as a loader bucket 16 b,one skilled in the art would realize that the return-to-dig mode can beused with other implements, such as a snow blade attachment, push broomattachment, and the like, attached to the boom assembly 17 of the workvehicle 10. System 90 is also operable in the horizon referencing modeby switching modes using switch 136.

[0060] In the horizon referencing mode, as illustrated in FIG. 1,controller 110 operates to maintain the orientation of implement 16parallel with the horizon H regardless of the orientation and positionof the boom assembly 17. In other words, at the moment that the horizonreferencing mode is activated using switch 136, controller 110 receivessignals from boom position sensor 140, optionally implement angleposition sensor 142, and vehicle tilt sensor 134, and uses thisinformation to operate electro-hydraulic implement cylinder valve 152 tomaintain the orientation of implement 16 parallel with the horizon H. InFIG. 1, implement 16 is shown oriented horizontal with the ground G asthe boom assembly 17 moves between positions A and B, and vice versa.One skilled in the art would realize that when the ground G is not flat,tilt sensor 134 provides signals to controller 110 so that thecontroller can take into account the position of the work vehicle 10relative to the horizon H in order to maintain implement 16 parallelwith the horizon. Subsequently, the operator is free to move the boomassembly 17 using either the enabled hand controls 60 or the enabledfoot pedal controls 50, and the controller 110 will maintain theorientation of implement 16 parallel with the horizon H throughout therange of motion of the boom assembly.

[0061] Thus, implement 16 is maintained parallel with the horizon H inresponse to signal input from tilt sensor 134, which may or may not meanthat implement 16 is maintained parallel to ground G. In the case whereground G and horizon H are parallel, as shown in FIG. 1, implement 16 ismaintained parallel to both the horizon and the ground. On the otherhand, when the ground G is not parallel with horizon H, such as occurswhen the work vehicle 10 is on the slope of a depression or a hill,system 90, operating in the horizon referencing mode, would keepimplement 16 parallel to horizon H, not ground G.

[0062] One skilled in the art would also realize that system 90 could bepracticed without vehicle tilt sensor 134; however, in this case thehorizon referencing mode would maintain the orientation of implement 16parallel to the frame of body 12 and not necessarily to the horizon.Clearly, it is preferred to practice system 90 with tilt sensor 134because there are operations wherein it is desirable to maintain theimplement 16 parallel to the horizon. One such operation is whenimplement 16 is a pallet forks lift attachment 16 a and it is desirableto keep the platform held by the forks lift level to the horizon toprevent spillage of materials off of the platform. However, one skilledin the art would realize that the horizon referencing mode could beselected when work vehicle 10 carries some other implement such as aloader bucket 16 b.

[0063] Controller 110 is connected to send electronic output signals forcontrol purposes, or for display purposes, depending upon the nature ofthe device receiving the output signals from the controller.Specifically, controller 110 is connected to send electronic controlsignals to electro-hydraulic valves 150, 152. Electronic control signalssent to boom cylinder valve 150 effect proportional control of hydraulicflow according to displacement of the left side operator controls,(i.e., either left foot control 50 or left hand control 60), so theelectro-hydraulic valve 150 activates a respective boom cylinder orcylinders 19, thereby collectively moving the boom assembly 17 betweendifferent positions such as positions A and B as shown in FIG. 1.Controller 110 also sends electronic control signals to implementcylinder valve 152 to effect proportional control of hydraulic flowaccording to displacement of the right side operator controls, (i.e.,either right foot control 50 or right hand control 60), so theelectro-hydraulic valve 152 activates a respective implement cylinder orcylinders 18, thereby collectively moving or rotating implement 16relative to the boom assembly 17.

[0064] Controller 110 is also connected to send electronic outputdisplay signals for activating indicators 139 on a status display 138.Preferably, indicators 139 are LEDs or light bulbs that light up whenactivated by output signals from controller 110; however, indicators 139can also be electronic gauges and the like for displaying informationuseful to an operator of the work vehicle 10.

[0065] Status display 138 is disposed on a portion of the TCS display 70as shown in FIG. 3. TCS display 70 also includes the hand/foot controlsselector switch 132, the vehicle tilt sensor 134, and the implementleveler mode switch 136. As shown in FIG. 2, the TCS display 70 ispositioned in cab 20 so as to be readily observable by the vehicleoperator. Preferably, the TCS display 70 is located in the upper frontportion of cab 20, although other locations in the cab are suitable aslong as the TCS display 70 is readily observable by the vehicleoperator.

[0066] Since the components of electronic control system 90 forcontrolling movement of boom assembly 17 and implement 16 have beendescribed in full detail, it is easy to understand the theory ofoperation for the control system 90 as will be described. Upon power-upof work vehicle 10, controller 110 prevents operator control over theboom assembly 17 and the implement 16 until the following enablingconditions are met: (a) the operator is seated in seat 22, therebyclosing seat switch 24; (b) restraint belt switch 26 is in the closedstate (i.e., male end 28 is secured to female end 30); and (c) thehand/foot controls selector switch 132 is pushed. When conditions (a),(b) and (c) are met, the controller 110 recalls from non-volatile memorystorage device 111 the last enabled operator control state of system 90,being either the first state wherein the hand controls 60 are enabled,or the second state wherein the foot controls 50 are enabled.Furthermore, upon power-up, controller 110 sends output signals tostatus display 138 so that a red LED 139 a will flash until the operatoris seated and has closed seat belt switch 26 and seat switch 24. Inaddition, until the operator pushes the hand/foot controls selectorswitch 132, a yellow LED 139 b flashes on status display 138.

[0067] Analog signals generated by hand control sensors 122, 124 andfoot control sensors 126, 128 are proportional to the displacement ofthe hand controls 60 and foot controls 50, respectively, from a neutralposition stored in the memory storage device 111. Based upon themagnitude of displacement of each control 50, 60 from the neutralposition, controller 110 routes hydraulic fluid flow in a proportionalmanner using electro-hydraulic valves 150, 152 to effect movement ofboom assembly 17 and implement 16. What the operator in the cabperceives is that displacement of enabled controls 50 or 60 affects boththe velocity of movement, and the position, of the boom assembly 17 andimplement 16.

[0068] Other preferred programmed features of system 90 include thatupon start-up the automatic self-leveling feature (also referred to asthe “implement leveler mode”) is defaulted to the null mode. Inaddition, controller 110 is programmed so that if the operator is out ofthe seat 22 for a time period exceeding a pre-determined time period,then the operator must re-sequence the “seat belt switch and seatswitch” circuit 120 and re-push the hand/foot controls selector switch132 in order to re-enable controller 110 to control hydraulic fluid flowthrough electro-hydraulic valves 150, 152.

[0069] Another preferred programmed feature of system 90 is that whenthe operator turns off the work vehicle 10 using an ignition key, or thelike, and does not leave the seat 22 (i.e., seat switch 24 remainsclosed) and the seat belt remains fastened (i.e., restraint belt switch26 remains closed), then controller 110 is programmed to automaticallyre-enable hydraulic fluid flow via valves 150 and 152 upon re-start ofthe vehicle 10 without the need for the operator to re-sequence the“seat belt switch and seat switch” circuit 120, and re-push thehand/foot controls selector switch 132.

[0070] Yet another preferred programmed feature of system 90 is that thehand/foot controls selector switch 132 can be operated to change thecontrol option from hand to foot, and vice versa, while work vehicle 10is powered up and operating.

[0071] While the present invention has been described with reference tocertain preferred embodiments, one of ordinary skill in the art willrecognize that additions, deletions, substitutions, modifications andimprovements can be made while remaining within the spirit and scope ofthe present invention as defined by the appended claims.

What is claimed is:
 1. An electronic control system for a machine havinga boom assembly and an implement assembly connected to the boomassembly, the control system comprising: a microprocessor having aninput and generating first and second output signals; a firstelectrohydraulic valve connected to receive the first output signal fromthe microprocessor, wherein the first electrohydraulic valve isconnected to position the boom assembly in response to the first outputsignal; a second electrohydraulic valve connected to receive the secondoutput signal from the microprocessor, wherein the secondelectrohydraulic valve is connected to position the implement assemblyin response to the second output signal; and a boom position sensordisposed on the boom assembly or the implement assembly and connected tosend a boom position input signal to the microprocessor, wherein themicroprocessor is connected to receive the boom position input signaland generate at least one of the first output signal and the secondoutput signal, thereby controlling a position of the implement assemblyrelative to the boom assembly.
 2. An electronic control system asrecited in claim 1, further comprising: a safety switch circuitconnected to send a first activation signal to the microprocessor,wherein the microprocessor is unable to generate the first output signaland is unable to generate the second output signal until themicroprocessor receives the first activation signal generated by thesafety switch circuit.
 3. An electronic control system as recited inclaim 2, wherein the safety switch circuit is connected to a seat belthaving male and female ends, and wherein the safety switch circuit sendsthe first activation signal when the male and female ends are securedtogether.
 4. An electronic control system as recited in claim 2, whereinthe safety switch circuit is connected to an operator's seat, andwherein the safety switch circuit sends the first activation signal whenan operator is sitting in the operator's seat.
 5. An electronic controlsystem as recited in claim 2, wherein the safety switch circuit isconnected to a seat belt having male and female ends, wherein the safetyswitch circuit is connected to an operator's seat, and wherein thesafety switch circuit sends the first activation signal when the maleand female ends of the seat belt are secured together and an operator issitting in the operator's seat.
 6. An electronic control system asrecited in claim 1, wherein the implement assembly is selected from thegroup consisting of a pallet fork lift assembly and a loader bucketassembly.
 7. An electronic control system as recited in claim 1, furthercomprising: a right hand stick implement control sensor disposed tosense a position of a right hand control; a left hand stick boom controlsensor disposed to sense a position of a left hand control; a right footpedal implement control sensor disposed to sense a position of a rightfoot pedal control; and a left foot pedal boom control sensor disposedto sense a position of a left foot pedal control, where each controlsensor is connected to send electronic signals to the microprocessor. 8.An electronic control system as recited in claim 7, further comprising:a hand/foot controls selector switch connected to send a first enablingsignal to the microprocessor, wherein the first enabling signal enablesthe microprocessor (a) to generate first and second output signals inresponse to electronic signals received from the right hand stickimplement control sensor and the left hand stick boom control sensor,and (b) but not to generate first and second output signals in responseto electronic signals received from the right foot pedal implementcontrol sensor and the left foot pedal boom control sensor.
 9. Anelectronic control system as recited in claim 8, wherein themicroprocessor generates the second output signal in response toelectronic signals received from the right hand stick implement controlsensor and generates the first output signal in response to electronicsignals received from the left hand stick boom control sensor.
 10. Anelectronic control system as recited in claim 8, wherein the hand/footcontrols selector switch is connected to send a second enabling signalto the microprocessor (a), wherein the second enabling signal enablesthe microprocessor to generate first and second output signals inresponse to electronic signals received from the right foot pedalimplement control sensor and the left foot pedal boom control sensor,and (b) but not to generate first and second output signals in responseto electronic signals received from the right hand stick implementcontrol sensor and the left hand stick boom control sensor.
 11. Anelectronic control system as recited in claim 7, further comprising: ahand/foot controls selector switch connected to send a first enablingsignal to the microprocessor, wherein the first enabling signal enablesthe microprocessor (a) to generate first and second output signals inresponse to electronic signals received from the right foot pedalimplement control sensor and the left foot pedal boom control sensor,and (b) but not to generate first and second output signals in responseto electronic signals received from the right hand stick implementcontrol sensor and the left hand stick boom control sensor.
 12. Anelectronic control system as recited in claim 11, wherein themicroprocessor generates the second output signal in response toelectronic signals received from the right foot pedal implement controlsensor and generates the first output signal in response to electronicsignals received from the left foot pedal boom control sensor.
 13. Anelectronic control system as recited in claim 11, wherein the hand/footcontrols selector switch is connected to send a second enabling signalto the microprocessor, wherein the second enabling signal enables themicroprocessor (a) to generate first and second output signals inresponse to electronic signals received from the right hand stickimplement control sensor and the left hand stick boom control sensor,and (b) but not to generate first and second output signals in responseto electronic signals received from the right foot pedal implementcontrol sensor and the left foot pedal boom control sensor.
 14. Anelectronic control system as recited in claim 8, further comprising: astatus display including a first light source connected to receive thirdoutput signals from the microprocessor, wherein the microprocessor sendsthe third output signals to control flashing of the light source untilthe microprocessor generates the first enabling signal.
 15. Anelectronic control system as recited in claim 11, further comprising: astatus display including a first light source connected to receive thirdoutput signals from the microprocessor, wherein the microprocessor sendsthe third output signals to control flashing of the light source untilthe microprocessor generates the first enabling signal.
 16. Anelectronic control system as recited in claim 2, further comprising: astatus display including a first light source connected to receive thirdoutput signals from the microprocessor, wherein the microprocessor sendsthe third output signals to control flashing of the light source untilthe microprocessor receives the first activation signal from the safetyswitch.
 17. An electronic control system as recited in claim 1, furthercomprising: an implement angle position sensor disposed to sense anangular position of the implement assembly relative to the machine andgenerate an implement angle position input signal, wherein themicroprocessor is connected to receive the implement angle positioninput signal from the implement angle position sensor; and wherein themicroprocessor generates at least one of the first output signal and thesecond output signal in response to receiving the boom position inputsignal and the implement angle position input signal.
 18. An electroniccontrol system as recited in claim 17, further comprising: a tilt sensordisposed on the machine to sense a position of the machine relative tothe horizon and generate a tilt input signal, wherein the microprocessoris connected to receive the tilt input signal from the tilt sensor, andwherein the microprocessor generates at least one of the first outputsignal and the second output signal in response to receiving the boomposition input signal, the implement angle position input signal, andthe tilt input signal.
 19. An electronic control system as recited inclaim 18, wherein the microprocessor is programmed to perform animplement self-leveling function operable in three modes in response toreceiving the boom position input signal, the implement angle positioninput signal, and the tilt input signal, wherein the first mode is anull mode, the second mode is a return-to-dig mode, and the third modeis a horizon referencing mode, and the electronic control system furthercomprises: an implement leveler mode selection switch connected to senda mode selection signal to the microprocessor, wherein themicroprocessor selectively operates in one of the null mode, thereturn-to-dig mode, and the horizon referencing mode in response toreceiving the mode selection input signal from the implement levelermode selection switch.